The Ecology of Fear

The largest living organism on earth is probably an Aspen grove. Aspen trees in a grove are genetically identical, usually born of the same parent tree, most often from roots that burrow under the earth. Seeking sun and life, they shoot through the earth and grow into the mountain sky. Others grow from seeds blown about on Autumn “Aspen Winds.” Wandering Rocky Mountain backpackers will go to sleep one evening after marveling at the golden leaves in an Aspen meadow and awake the next morning to find that the nighttime Aspen winds stripped the trees bare.

Probably every bird that lives in or travels through the Rocky Mountains has perched in an Aspen tree, an example of how every living being, most assuredly including humans, on this planet is connected in some way.

Aspen tree bark is to Elk what chocolate is to humans: A great treat which; although strictly speaking, is unnecessary to sustain life, makes life richer. Elk, unlike humans, lack self-restraint. Left to themselves they will strip the bark off an Aspen tree. Naked Aspen trees, like naked humans, will die in a Rocky Mountain winter.

And that has been a problem in Yellowstone National Park and other places in the Rockies since mankind decided to eradicate wolves. Recently we looked at a book by the publishers of Outdoor Life, written in the early 1950’s. In it was a painting of a wolf, along with an article which ended looking forward to the day when a hunter shot the last living wolf for, “The only good wolf is a dead wolf.” There is no doubt that the author of the piece was filled with the best of intentions, believing wolves pestilential.

As is so often the case in humanity’s history, we are reminded of a well-known road paved with good intentions.

We pretty much eradicated wolves from Yellowstone and the Rockies. But wolves eat elk. About one a month per wolf. Because the wolves were gone, elk lost their main predator and multiplied in great numbers. Lacking self-restraint, they ate Aspens at a prodigious rate. The Aspens died. Soon Yellowstone was almost bereft of Aspens. Birds lost protected perches where they could rest from their arduous migrations but still have a good field of view to protect themselves from their predators.

Then recently humans began allowing wolves back into Yellowstone. Not very many, certainly not enough to cull the immense Elk herds which were destroying the Aspen, but enough to introduce what one biologist calls, “the ecology of fear.” It turns out that Elk can exercise a form of self-restraint: They won’t go deep into Aspen groves if they are afraid of wolves. Deep in an Aspen grove, as you can see, elk lack a wide field of view from which they can see approaching wolves. So they eat Aspen bark only on the edges of groves and they eat it quickly. They don’t take time to completely strip even the trees on the edge of the grove. The trees are returning to health and the songs of birds can again be heard in Aspen groves.

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This entry was posted on August 7, 2007 at 8:24 pm and is filed under Ecology. You can follow any responses to this entry through the RSS 2.0 feed.
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